def ds_open(self,extent):
assert isinstance(extent,Extent),\
"%s 'extent' argument must be a fbadscb.Extent object: %s" \
% (eloc(self,"ds_open",module=this_module),extent)
if self.extent:
raise NotImplementedError("%s extent already open: %s" \
% (eloc(self,"ds_open",module=this_module),self.extent))
self._ck_extent(extent)
self.extent=extent # Remember the physical extent
self.lower=extent.lower # The first physical sector of the extent
self.upper=extent.upper # The last physical sector of the extent
self.ds_sector=0 # The next logical sector to be accessed
self.ds_sectors=extent.sectors() # Calculate the number of sectors
self.ds_last=self.ds_sectors-1 # The last logical sector in the extent
# Trace the data set open if tracing is enabled
if __debug__:
if self._trace:
print("%s DS_OPEN: extent:%s sectors:%s logical sectors:0-%s" \
% (eloc(self,"ds_open",module=this_module),\
extent,self.ds_sectors,self.ds_last))
self.seek(self.lower) # Position at start of the extent
def seek(self,sector):
# Determine the position in the file for a physical sector access
if sector>self.last:
raise ValueError("%s FBA sector %s is beyond last sector %s" \
% (eloc(self,"seek",module=this_module),sector,self.last))
sector_loc=sector*512
if sector_loc>self.filesize:
raise IOError("%s FBA sector %s file position %s is beyond EOF: %s" \
% (eloc(self,"seek",module=this_module),sector,sector_loc,\
self.filesize))
# Perform the positioning by physical sector number in this object and
# position the file object accordingly
try:
self.fo.seek(sector_loc)
except IOError:
raise IOError("%s IOError while positioning to FBA sector: %s" \
% (eloc(self,"seek",module=this_module),self.sector))
self.sector=sector
# Trace the seek if physical tracing is enabled
if __debug__:
if self._trace:
print("%s SEEK: sector: %s file pos: %s" \
% (eloc(self,"seek",module=this_module),sector,self.fo.tell()))
def ds_tell(self):
if not self.extent:
raise NotImplementedError("%s no open extent for logical sector position" \
% (eloc(self,"ds_tell",module=this_module)))
if __debug__:
if self._trace:
print("%s returning: %s" \
% (eloc(self,"ds_tell",module=this_module),self.ds_sector))
return self.ds_sector
def _to_physical(self,sector,sectors=1):
assert sector >=0,"%s 'sector' argument must be >= 0: %s" \
% (eloc(self,"_to_physical",module=this_module),sector)
assert sectors >=1,"%s 'sectors' argument must be >= 1: %s" \
% (eloc(self,"_to_physical",module=this_module),sectors)
l_last=sector+sectors-1
if l_last > self.upper:
raise ValueError(\
"%s end of operation beyond end of extent (%s): %s" \
% (eloc(self,"_to_physical",module=this_module),\
self.upper,l_last))
return (self.lower+sector,self.lower+l_last,l_last)
def ds_erase(self,sector=0,sectors=1,fill=0):
assert isinstance(sector,int) and sector>=0,\
"%s 'sector' argument must be an integer >= 0: %s"\
% (eloc(self,"ds_erase",module=this_module),sector)
if self.ro:
raise NotImplementedError("%s can not erase a read-only image file: %s"\
% (eloc(self,"ds_erase",module=this_module),self.filename))
if not self.extent:
raise NotImplementedError("%s no open extent for erasing" \
% (eloc(self,"ds_erase",module=this_module)))
# Create the content for an erased sector
if isinstance(fill,str):
if len(fill)>0:
f=ord(fill[0])
else:
raise ValueError("%s 'fill' argument must not be an empty string"\
% eloc(self,"ds_erase",module=this_module))
elif isinstance(fill,int):
if fill<0 or fill >255:
raise ValueError("%s 'fill' argument out of range (0-255): %s" \
% eloc(self,"ds_erase",module=this_module),fill)
f=fill
byts=bytes([f,]*512)
# Determine the physical sectors of erased area
if sectors == True:
secs=self.ds_sectors
else:
assert isinstance(sectors,int) and sectors>=1,\
"%s 'sectors' argument must be True or an integer >= 1: %s" \
% (eloc(self,"ds_erase",module=this_module),sectors)
secs=sectors
p_first,p_last,l_last = self._to_physical(sector,sectors=secs)
# Erase the requested sectors' content
self.seek(p_first)
sec=sector
if __debug__:
if self._trace:
if secs == 1:
s="%s DS_ERASING: logical sector:%s physical sector: %s"\
"file pos:%s with:%02X" \
% (eloc(self,"ds_read",module=this_module),\
sector,p_first,self.fo.tell(),f)
else:
s="%s DS_ERASING: logical sectors:%s-%s physical sectors: %s-%s" \
" sectors:%s file pos:%s with:0x%02X" \
% (eloc(self,"ds_read",module=this_module),\
sector,l_last,p_first,p_last,secs,self.fo.tell(),\
f)
print(s)
# Erase the requested sectors' content
for n in range(secs):
self._write(byts)
self.sector+=1
self.ds_sector+=1
def _ck_extent(self,extent):
if extent.notused:
raise ValueError("%s Extent object must be used: %s" \
% (eloc(self,"_ck_extent",module=this_module),extent))
lower=extent.lower
if lower>self.last:
raise ValueError(\
"%s extent lower boundary is not within the FBA image (0-%s): %s"\
% (eloc(self,"_ck_extent",module=this_module),self.last,lower))
upper=extent.upper
if upper>self.last:
raise ValueError(\
"%s extent upper boundary is not within the FBA image (0-%s): %s"\
% (eloc(self,"_ck_extent",module=this_module),self.last,upper))
def read(self,sector=None,array=False):
# Position the image file if requested to do so.
if sector is not None:
self.seek(sector)
# Trace the read if physical tracing is enabled
if __debug__:
if self._trace:
sec=self.sector
fpos=self.fo.tell()
# Read the physical sector using the low-level routine
data=self._read(512)
self.sector+=1
# Trace the read if physical tracing is enabled
if __debug__:
if self._trace:
print("%s READ: sector: %s file pos: %s" \
% (eloc(self,"read",module=this_module),sec,fpos))
if self._tdump:
dump(data,indent=" ")
# Return the information is the requested sequence type
if array:
return bytearray(data)
return data
def ds_write(self,byts,sector=None):
if self.ro:
raise NotImplementedError("%s can not write to a read-only image file: %s"\
% (eloc(self,"ds_write",module=this_module),self.filename))
if not self.extent:
raise NotImplementedError("%s no open extent for writing" \
% (eloc(self,"ds_write",module=this_module)))
# Validate there is enough data to write entire sectors
try:
sectors=bytes2sectors(byts)
except ValueError:
raise ValueError("%s 'byts' argument not full sectors, length: %s" \
% (eloc(self,"ds_write",module=this_module),len(byts))) from None
# Locate where the write operation begins
if sector is None:
sec=self.ds_sector
else:
sec=sector
p_first,p_last,l_last=self._to_physical(sec,sectors=sectors)
# Position to the starting sector
self.seek(p_first)
self.ds_sector=sec
# Perform tracing if requested.
if __debug__:
if self._trace:
if sectors == 1:
s="%s DS_WRITE: logical sector:%s physical sector: %s"\
"file pos: %s" % (eloc(self,"ds_write",module=this_module),\
sector,p_first,self.fo.tell())
else:
s="%s DS_WRITE: logical sectors:%s-%s physical sectors: %s-%s" \
"sectors:%s file pos:%s" \
% (eloc(self,"ds_write",module=this_module),sector,\
l_last,p_first,p_last,sectors,self.fo.tell())
print(s)
if self._tdump:
dump(byts,indent=" ")
# Write the sector' or sectors' content
self._write(byts)
self.sector+=sectors
self.ds_sector+=sectors
def trace(self,state,dump=False):
if state:
self._trace=True
self._tdump=dump
if __debug__:
print("%s set tracing:%s, dump:%s" \
% (eloc(self,"trace",module=this_module),self._trace,self._tdump))
else:
if __debug__:
was_tracing=self._trace
self._trace=False
self._tdump=False
if __debug__:
if was_tracing:
print("%s set tracing:%s, dump:%s" \
% (eloc(self,"trace",module=this_module),\
self._trace,self.dump))
def detach(self):
if __debug__:
if self._trace:
print("%s detaching image file: %s" \
% (eloc(self,"detach",module=this_module),self.filename))
if self.extent:
self.ds_close()
try:
self.fo.flush()
self.fo.close()
except IOError:
raise IOError(\
"%s IOError detaching %s FBA image: %s" \
% (eloc(self,"detach",module=this_module),self.filename))
self.pending=False
def ds_read(self,sector=None,sectors=1,array=False):
if not self.extent:
raise NotImplementedError("%s no open extent for reading" \
% eloc(self,"ds_read",module=this_module))
if sector is None:
sec=self.ds_sector
else:
sec=sector
p_first,p_last,l_last=self._to_physical(sec,sectors=sectors)
# Position to the starting sector
self.seek(p_first)
self.ds_sector=sec
# Perform tracing if requested
if __debug__:
if self._trace:
if sectors == 1:
s="%s DS_READ: logical sector:%s physical sector: %s"\
" file pos:%s" % (eloc(self,"ds_read",module=this_module),\
sec,p_first,self.fo.tell())
else:
s="%s DS_READ: logical sectors:%s-%s physical sectors: %s-%s" \
" sectors:%s file pos: %s"\
% (eloc(self,"ds_read",module=this_module),\
sec,l_last,p_first,p_last,sectors,self.fo.tell())
print(s)
# Read the sector' or sectors' content
byts=self._read(sectors*512)
self.sector+=sectors
self.ds_sector+=sectors
# Dump the content read from the file image if content tracing enabled
if __debug__:
if self._tdump:
dump(byts,indent=" ")
# Return the content read from the sector or sectors as bytes or bytearray
# as requested.
if array:
return bytearray(byts)
return byts
def _read(self,size):
# Force writing any pending writes before attempting to read the file
# otherwise, the image file may have stale sector data.
if self.pending:
# By using this method we get to trace the flush operation
self.flush()
# Read the requested bytes
try:
byts=self.fo.read(size)
except IOError:
raise IOError("%s IOError while reading FBA physical sector: %s" \
% (eloc(self,"_read",module=this_module),self.sector))
# Ensure we actually read the number of expected bytes.
if len(byts)!=size:
raise ValueError(\
"%s did not read requested bytes (%s) from image file: %s"
% (eloc(self,"_read",module=this_module),size,len(byts)))
return byts
def _write(self,data):
# Ensure bytes sequence is being written not bytearray. Python requires
# a bytes sequence. Sequence can not be bytearray. This give the using
# software the freedom to use either sequence.
if isinstance(data,bytearray):
byts=bytes(data)
else:
byts=data
assert isinstance(byts,bytes),\
"%s 'data' argument must be a bytes/bytearray sequence for sector %s: %s" \
% (eloc(self,"_write",module=this_module),byts,self.sector)
# Write the bytes
try:
self.fo.write(byts)
except IOError:
raise IOError(\
"%s IOError while writing FBA physical sector: %s" \
% (eloc(self,"write",module=this_module),self.sector))
self.pending=True # Indicate the write might be pending
def ds_extent(self,lower,upper):
if upper is True:
up=self.last
else:
up=upper
ext=Extent(lower=lower,upper=up)
if __debug__:
if self._trace:
print("%s returned: %s" % (eloc(self,"ds_extent"),ext))
return ext
def ds_close(self):
# Trace the data set close if logical sector tracing is enabled
if __debug__:
if self._trace:
print("%s DS_CLOSE: closing extent: %s" \
% (eloc(self,"ds_close",module=this_module),self.extent))
if self.extent:
self.flush() # Write any pending sectors to the image file
self.ds_sector=self.ds_last=self.extent=self.lower=self.upper=None
self.ds_sectors=0
def write(self,byts,sector=None,pad=False):
if self.ro:
raise NotImplementedError(\
"%s can not write to read-only FBA image: %s" \
% (eloc(self,"write",module=this_module),self.filename))
# Position the image file if requested to do so.
if sector is not None:
self.seek(sector)
# Pad or detect truncated sector content
data=byts
if len(data)!=512:
if pad:
data=data+fba.pad
data=data[:512]
else:
raise ValueError("%s FBA image sector must be 512 bytes: %s"\
% (eloc(self,"write",module=this_module),len(data)))
# Trace the write operation if physical sector tracing is enabled
if __debug__:
if self._trace:
if len(data)>len(byts):
padded=" pad: %s" % len(data) - len(byts)
else:
padded=""
print("%s WRITE: sector: %s file pos: %s%s" \
% (eloc(self,"write",module=this_module),\
sector,self.fo.tell(),padded))
if self._tdump:
dump(data,indent=" ")
# Write to the sector using the low-level routine
self._write(data)
self.sector+=1
def tell(self):
if __debug__:
if self._trace:
print("%s returning: %s" % (eloc(self,"tell",module=this_module),\
self.sector))
return self.sector
def flush(self):
if __debug__:
if self._trace:
print("%s forcing pending image file writes" \
% eloc(self,"flush",module=this_module))
self._flush() # Use the low-level method to actually force pending writes
